Magnetic fluid clutch with laminated structure



Aug. 16, 1966 J. s. BARRETT 3,266,606

MAGNETIC FLUID CLUTCH WITH LAMINATED STRUCTURE Original Filed May 21,1962 INVENTOR. J OHN S. BH/PA'TT i United States Patent 3,266,606MAGNETIC FLUID CLUTCH WITH LAMINATED STRUCTURE John S. Barrett, ChagrinFalls, Ohio, assignor to Sperry Rand Corporation, New York, N.Y., acorporation of Delaware Continuation of application Ser. No. 196,347,May 21,

1962. This application Sept. 24, 1964, Ser. No. 404,544

5 Claims. (Cl. 192-215) This application is a continuation of myco-pending application Serial No. 196,347 for Control Systems which wasfiled May 21, 196 2, and now abandoned.

This invention relates to improvements in control systems. Moreparticularly, this invention relates to improvements in magneticcircuits for electromagnetic devices.

It is, therefore, an object of the present invention to provide animproved magnetic circuit for an electromagnet device.

In the operation of an electromagnetic device, such as anelectromagnetic clutch or electromagnetic brake which uses magneticparticles, a voltage is selectively applied to ,the coil of that deviceto selectively force current to how through that coil. That current willcause that coil to generate a magnetic field which will enable themagnetic particles to apply forces to the relatively-rotatable parts ofthat device; and those forces will enable that device to perform itsintended function. The magnetic particles will substantially fill theworking gap between the relativelyrotatable parts of that device, andwill thus reduce the reluctance of that gap. Consequently, While thatworking gap will constitute a necessary and unavoidable reluctance inthe magnetic circuit of the electromagnetic device, the reluctance ofthat gap will be small.

The magnetic circuits of many electromagnetic devices, such aselectromagnetic clutches or electromagnetic brakes which use magneticparticles, have gaps in addition to the working gaps thereof, and thoseadditional gaps are objectiona'ble because they increase the amounts ofpower that are needed to operate those electromagnetic devices. It wouldbe desirable to eliminate all additional gaps from the magnetic circuitof an electromagnetic device, such as an electromagnetic clutch orelectromagnetic brake which uses magnetic particles, because theelimination of all such additional gaps would decrease the amount ofpower needed to operate that electromagnetic device. Such a decrease inpower would make the operation of that electromagnetic device moreeconomic, and would also decrease the heating of that electromagneticdevice. The present invention makes it possible to eliminate alladditional gaps from the magnetic circuit of an electromagnetic device,such as an electromagnetic clutch or electromagnetic brake which usesmagnetic particles; and thereby makes it possible to reduce the amountof power needed to operate that electromagnetic device. It is,therefore, an object of the present invention to eliminate alladditional gaps from the magnetic circut of an electromagnetic device,such as an electromagnetic clutch or electromagnetic brake usingmagnetic particles.

The pole pieces of electromagnetic devices, such as electromagneticclutches or electromagnetic brakes which use magnetic particles, arecustomarily made as solid pieces of magnetic material. The use of suchsolid pieces of magnetic material causes those electromagnetic devicesto have long time constants. As a result, it is not uncommon forelectromagnetic devices, such as electromagnetic clutches orelectromagnetic brakes which use magnetic particles and which have polepieces of solid magnetic material, to have time constants of severalhundred milliseconds. In many instances, a time constant of severalhundred milliseconds is objectionably long; and hence it I would bedesirable to provide an electromagnetic device,

Patented August 16, 1966 such as an electromagnetic clutch orelectromagnetic brake which uses magnetic particles, that has a shorttime constant. The present invention provides an electromagnetic device,such as an electromagnetic clutch or electromagnetic brake which usesmagnetic particles, that has a short time constant; and it does so byforming the pole pieces of that electromagnetic device from laminationsof magnetic material. It is, therefore, an object of the presentinvention to form the pole pieces of an electromagnetic device, such asan electromagnetic clutch or electromagnetic brake which uses magneticparticles, from laminations of magnetic material.

An electromagnetic device, such as an electromagnetic clutch orelectromagnetic brake which uses magnetic particles, customarily has awinding mounted on one of the relatively-rotatable parts thereof; andthat winding customarily provides only a small number of magnetic poles.As a result, the other relatively-rotatable part of that electromagneticdevice must have a large mass to enable it to have a low reluctance. Alarge mass for that other relatively-rotatable part means that the saidpart will have a large moment of inertia; and such a moment of inertiacan means a long response time for that electromagnetic device. Oneembodiment of the present invention makes it possible to reduce the massof the other relativelyrotata'ble part of an electromagnetic device,such as an electromagnetic clutch or electromagnetic brake which usesmagnetic particles, and thus makes it possible to reduce the moment ofinertia of that part by providing a multiplicity of poles for the onerelatively-rotatable part of that electromagnetic device. Themultiplicity of poles for that one part makes it possible to reduce thenumber of flux lines per pole and still have the same total overall fiuXdensity. With a reduced number of flux lines per pole, the mass of theother relatively-rotatable part of the electromagnetic device can bereduced, with a resulting overall shortening of the response time ofthat electromagnetic device. It is, therefore, an object of the presentinvention to provide an electromagnetic device, such as anelectromagnetic clutch or electromagnetic brake using magneticparticles, with a multiplicity of poles.

The poles of the said one embodiment of electromagnetic device providedby the present invention alternate in polarity; and this is desirablebecause it reduces the overall lengths of the flux paths in the otherrelatively-rotatable part of that electromagnetic device. The resultingshort flux paths enable that other relatively-rotatable part to having alow reluctance even though the said paths have small cross sections. Theoverall result is that the mass and the moment of inertia of the otherrelatively-rotatable part of an electromagnetic device can bereducedwith consequent shortening of the response time of thatelectromagnetic device. It is, therefore, an object of the presentinvention to provide an electromagnetic device, such as anelectromagnetic clutch or electromagnetic brake which uses magneticparticles, with poles of alternating polarity.

The rotors of the electromagnetic devices provided by the presentinvention have annuli of magnetic material and have narrow Webs thatsupport those annuli. Those annuli confront, and are closely adjacent,the stators of those electromagnetic devices; and those annuli aresubstantially co-extensive with those stators. The masses of the annuliare made as small as practicable and the masses of the webs also aremade small. In this way, the response times of the electromagneticdevices provided by the present invention are additionally shortened.

Other and [further objects and advantages of the present inventionshould become apparent from an examination of the drawing andaccompanying description.

In the drawing and accompanying description, two preferred embodimentsof the present invention are shown and described but it is to beunderstood that/the draw-ing and accompanying description are for thepurpose Olf illustration only and do not limit the invention and thatthe invention will be defined by the appended claims.

In the drawing, FIG. 1 is a partially-broken, and elevational View ofone embodiment of electromagnetic device that is made in accordance withthe principles and teaching of the present invention,

FIG. 2 is a partially-sectioned, side elevational view of theelectromagnetic device of FIG. 1, and it is taken along the broken planeindicated by the broken line 22 in FIG. 1,

FIG. 3 is a partially broken, and elevational view of a secondembodiment of electromagnetic device that is made in accordance with theprinciples and teachings Olf the present invention, and

FIG. 4 is a partially-sectioned, side elevational view of theelectromagnetic device t FIG. 3, and it is taken along the broken planeindicated by the broken line 4-4 in FIG. 3.

Referring to the drawing in detail, the numeral 22 denotes the stator ofone embodiment of electromagnetic device that is made in accordance withthe principles and teachings of the present invention. That statorconsists of a number of thin annular laminations of magnetic material,as [for example steel. Those laminations will be suitably insulated tromeach other by layers otf oxide thereon or by layers of insulating paintor the like between them. Those laminations can be suitably held inassembled relation by rivets or bolts or other means, not shown.

The stator 22 has a number of circumterentially-spaced slots 24 therein,and those slots define teeth 26. Also, those slots accommodate the turnsOlf a winding 28. The inner ends of the teeth 26 are elongated, in thecircumterential direction, and those inner ends partially close theslots 24. The winding 28 has turns thereof disposed within each or theslots 24; and that winding is rformed so adjacent poles are of oppositepolarity. The winding 28 can be made as one continuous winding or can bemade as a number or separate windingsthe principal requirements of thewinding 28 being that it make the adjacent poles Otf opposite polarityand that it provide the required total number of flux lines.

After the winding 28 has been disposed within the slots 24, -a pottingcompound 29 will be used to [fill the remaining spaces in those slots.That potting compound also will extend outwardly beyond the faces of thelefthandmost and the right-handmost laminations of the stator 22, andwill enclose and embed the end turns otf the winding 28. Further, thatpotting compound will pro- Wide a wear-resistant annulus which will helpdefine the open area in the interior of the housing for theelectromagnetic ldevice. Different potting compounds could be (used, butthe epoxy resins are preferred. The potting compound will be ttormed ina suitable mold.

The housing tor the electromagnetic device of the present inventionincludes cup-like members 30 and '32 Off magnetic or non-magneticmaterial. The inner periphcries of those members are approximately equalto the outer diameter of the stator 22; and those cup-like members canbe pressed onto that stator. The potting compound 29 will be formed sothe end (faces and the periphery thereof, will closely abut the innerfaces of the cupiike members 30 and 32.

The cup-like member '30 has an annular socket 34, and

the cup-like member \32 has an annular socket 36. Those sockets are inregister with each other, and they accommodate the outer races ofantifriction bearings 68 and a 40, respectively. The inner races 0tthose anti-friction bearings accommodate reduced-diameter portions or ahollow shaft 42. That hollow shaft has a keyway 44 which will enable itto be locked against rotation relative to a shaft which is telescopedinto it. The hollow shaft 42 also has a threaded opening 45 which canaccommodate a set screw, and that set screw can bear against the shaftwhich will be telescoped through that hollow shaft.

The hollow sharft 42 has a centrally-located portion 46 01f greaterthickness, and that portion provides shoulders against which the innerraces of the anti-friction bearings 38 and 40 can be pressed. A web 48is suitably secured to the portion 46 of increased thickness, as bybrazing or welding; and that web has openings 49 therein, as shownparticularly by FIG. 2. Axially-extending clamps 50 are suitably securedto the web 4 8, as by brazing or welding, and those clamps projectoutwardly from each (face or that web. The ends of those clamps extendradially out-' 7 wardly toward the winding 28; and those clamps hold anannulus 52 of magnetic material. That annulus consists of a number ofthin annular laminations of magnetic material, such as steel; and thoselaminations will be suitably insulated trom each other by layers ofoxide thereon or by layers of insulating paint or the like between them.The clamps 50 hold the laminations of the magnetic annulus 52 inintimate engagement with each other and hold them substantially inregister with the laminations of the stator 22.

Slingers 54 are mounted on the portion 46 of increased thickness of thehollow shaft 42; and those slingers are mounted inwardly of the antifriction bearings 38 and 40. Magnetic particles 66 are disposed withinthe housing ot the electromagnetic device of FIGS. 1 and 2; and most ofthose magnetic particles will be disposed within and adjacent to theworking gap between the stator 22 and the magnetic annulus 52. Tofacilitate a clear showing of the relatively-rotatable parts in FIG. 2,the magnetic particles 56 are not shown in FIG. 2. Those magneticparticles are of standard and usual size, form and composition; andenough of those magnetic particles are provided to more than fill theworking gap between the stator 22 and the annulus 52 of magneticmaterial. The slingers 5 4 are intended to cause any magnetic particles56, that tend to work their way into the anti-friction bearings 38 and40, to be thrown radially outwardly toward the working gap. The magneticlines of force generated by the winding 28 will then be able to attractthose magnetic particles and to keep them \from passing into theanti-friction bearings 38 and 40.

The radially-directed dimensions of the laminations of the annulus 52 ofmagnetic material are preferably equal to one-half of the widths of thenarrowest portions of the laminations of the stator 22. Such anarrangement is important in reducing the mass and moment of inertia ofthe rotor, which includes the hollow shaft 42, the slingers 54, the web48, and the annulus 52 of magnetic material. The radially-directeddimensions of the laminations of the annulus 52 of magnetic material canbe made that small because each pole of the stator 22 is of alternatepolarity; and the alternations of the polarities of those poles causethe flux lines passing radially inwa-rdly through any given pole todivide the flow in opposite directions through the annulus 52 ofmagnetic material, thereby making the number or" flux lines flowingthrough each section of that annulus about one-half of the number offlux line flowing through that pole.

The multiplicity of poles 26 that is provided for the stator 22 isimportant, because it very materially reduces the lengths of the fluxpaths through the annulus 52 of magnetic material. For example, magneticflux lines passing radially inwardly through a given pole will passthrough the magnetic particles 56 in the working gap between the stator2-2 and the annulus 52; and then half of those flux lines will movethrough that annulus in the clockwise direction until they are inregister with thenext clockwise pole while the rest of those flux lineswill move in the counter clockwise direction through that annulus untilthey are in register with the next counter clockwise pole, andthereatater those flux lines will move radially outwardly through theworking gap and into.

those poles. The overall result is that the magnetic flux lines havevery short paths through the annulus 52 of magnetic material. Theshortness of those paths makes it possible to reduce the cross section,and thus the mass, of the annulus 52 of the electromagnetic device shownin FIGS. 1 and 2.

The Web 48 is thin and thus has a small mass; and that small mass isadditionally reduced by the presence of the openings 49. The overallresult is that the mass and moment of inertia of the rotor of theelectromagnetic device of FIGS. 1 and 2 are small. 1

The electromagnetic device of FIGS. 1 and 2 is adapted for use as anelectromagnetic brake; and where that electromagnetic device is to beused as an electromagnetic brake, the hollow shaft 42 will be telescopedover and secured to a rotatable shaft, not shown, and the housing willbe suitably held stationary. As long as the winding 28 remainsde-energized, the hollow shaft 42 will be able to rotate freely relativetothe housing of the electromagnetic device; and hence the shaft, notshown, will be able to rotate freely relative to that housing. However,when current is caused to flow through the winding 28, magnetic fluixlines will flow through each odd-numbered pole, across the working gapinto the annulus 52, through portions of that annulus, and then backacross that Working gap into the even-numbered poles. Those magneticflux lines will hold most of the magnetic particles 56 within thatworking gap; and those magnetic particles will apply forces to thestator 22 and to the annulus 52 which will cause the hollow shaft 42 totend to come to rest. The amount of current flowing through the wind ing28 will determine the amount of breaking force which the magneticparticles 56 can apply to the hollow shaft 42. Preferably, the winding28 will be made so sufficient current can flow through it to enable themagnetic flux lines to coact with the particles 56 of magnetic materialto prevent relative rotation between the hollow shaft 42 and thehousing.

The electromagnetic device of FIGS. 1 and 2 can be modified so it willbe adapted for use as an electromagnetic clutch. Specifically, thatdevice can be made so the winding thereof will be mounted on the rotor,so the housing thereof is rotatable, and so that housing includes anannulus, of magnetic material, that has a small cross section. Thatrotor will have a multiplicity of slots therein, and the winding will bedisposed within those slots to generate a multiplicity of magneticpoles. The odd-numbered poles will 'be of one polarity, and theevennumbered poles will be of opposite polarity. Suitable slip rings andbrushes will be providedto conduct current to that winding. The housingand its annulus of magnetic material will have a small mass. Thathousing will be suitably secured to a driven member, not shown, and thehollow shaft 42 will be telescoped over and secured to a driving shaft,not shown. As long as the winding remains de-energized the drivingshaft, not shown, will be able to rotate freely relative to the drivenmember, not shown. However, when current is caused to flow through thatwinding, magnetic flux lines will flow through each old-numbered pole,across the working gap into the annulus of the housing, through portionsof that annulus, and then back across that working gap into theeven-numbered poles. Those magnetic fi-ux lines will hold most of themagnetic particles within that working gap; and those magnetic particleswill apply forces to the rotor and to the annulus which will force thehousing to rotate with the hollow shaft 42-and thus force the drivenmember to rotate with the driving shaft.

The only gap for the magnetic flux lines in the electromagnetic deviceof FIGS. 1 and 2, and in the modified form of that electromagneticdevice, is the working gap between the confronting faces of therelatively-rotatable parts. As a result, the electromagnetic device ofFIGS. 1 and 2, and the modified form of that elect-romagnetic device,are completely free of the additional gaps in the direction of flow offlux lines commonly found in electromagnetic devices which use magneticparticles.

The laminating of the stator 22 and of the annulus 52, the provision ofa multiplicity of poles for that stator, the alternation of thepolarities of those poles, theuse of an annulus of narrow cross section,and the use of a thin Web to support that annulus make it possible toprovide a time constant for the electromagnetic device of FIGS. 1 and 2which is much shorter than the time constant of a conventionalelectromagnetic device using magnetic particles. Specifically, aconventional electromagnetic device with a torque rating of twentypoundafeet has an overall time constant of about three hundredmilliseconds; but the electromagnetic device of FIGS. 1 and 2 can bemade to produce the same torque rating and yet have an overall timeconstant of less than fifteen milliseconds. In

fact, the electromagnetic device of FIGS. 1 and 2 can have an overalltime constant of only fourteen milliseconds whenever D.C. is used toenergize the winding 28 and can have an overall time constant of aslittle as ten milliseconds whenever AC. is used to energize thatwinding.

In assembling the electromagnetic device of FIGS. 1 and 2, thelaminations of the stator 22 are suitably punched and are then assembledtogether. Thereafter, the winding 28 is wound into the slots of thatstator. The stator 22 and its winding 28 are then placed within a mold,and the potting compound will then be used to embed that winding.

The web 48 is secured to the hollow shaft 42, as by welding; and theslingers 54 are then secured to that hollow shaft. The clamps 50 at oneside of that web are suitably secured to that web, as by brazing.Thereafter, the laminations of the annulus 52 are set in engagement witheach other and with the clamps 50 at the one side of the web 48; andthereupon the clamps 50 at the other side of that web are secured tothat web, as by brazing.

The cup-like portion 30 of the housing is then pressed onto the stator22, and the anti-friction bearing 38 is pressed onto the left-hand endof the hollow shaft 42. Thereafter, that shaft and the Web 48 and theannulus 52 will be telescoped into the open right-hand end of thehousing until the outer race of the bearing 38 engages and is held bythe annular socket 34 of the cup-like portion 30 of the housing. Theinner race of the anti-friction bearing 40 is then telescoped over theright-hand end of the hollow shaft 42; and then the cup-like portion 32of the housing can be pressed onto the stator 22 while the socket 36 ispressed onto the outer race of the antifriction bearing 40.

Referring to FIGS. 3 and 4, the numeral 60 denotes a stator which isformed from a large number of laminations of magnetic material such assteel. Those laminations are elongated and narrow, and they are set inface-to-face relation to define an annulus. That annulus abuts the innerface of an annular housing 62 of non-magnetic material. An end plate 64of annular configuration is telescoped within one end of the annulusdefined by the stator 60, and an end plate 66 of annular configurationis telescoped within the other end of that stator. The end plate 66 hasa sheave-like projection 67 thereon. Those end plates are made fromnon-magnetic material.

The end plate 64 has an annular socket 68 therein, and the end plate 66has an annular socket 70 therein. Those sockets are in register witheach other; and they accommodate anti-friction bearings 71 and 72,respectively. A hollow shaft 76 has portions of reduced thickness whichare accommodated by the inner races of the anti-friction bearings 71 and72. That hollow shaft has a keyway 78, as shown particularly by FIG. 4;and that keyway can receive a key which will prevent relative rotationbetween that lhOHOW shaft and a shaft, not shown, which can betelescoped within that hollow shaft. A set screw 79 is mounted within athreaded opening 81 in the shaft 76,

d and that set screw can help prevent relative rotation between thathollow shaft and the shaft, not shown.

The hollow shaft 76 has a portion 80 of increased thickness; and thatportion provides two shoulders which can receive the inner races of theanti-friction bearings 71 and 72. The hollow shaft 76 has a passageway82 which extends through it, and it has a sleeve 84 which is fixedlysecured to it, as by a set screw 85. The sleeve 84 hasradially-extending passages therein which communicate with the passage82 in the hollow shaft 76. Slip rings 86 are disposed incircumferentially-extending grooves in the face of the sleeve 84, andthose circumferentiallyextending grooves communicate with theradially-extending passages in that sleeve.

The numeral 88 denotes a web that is secured to the portion 80 ofincreased thickness of the hollow shaft '76, as by a weld. That web ismade thin to reduce the mass thereof, and it is provided with openings89 to further reduce the mass thereof. That web supports an annulus 90which is made up of a large number of laminations of magnetic materialsuch as steel. Those laminations are mounted in intimate face-to-facerelation-ship, as indicated by FIG. 4. The periphery of the web 88 abutsthe inner faces of each of the laminations of the annulus 90, and thatperiphery will be suitably secured to those laminations as by brazing.

Each of the laminations of the annulus 90 has a recess in the outer edgethereof, and those recesses coact to define an annular recess 92 in theperiphery of the annulus 90. A winding 94 is disposed within thatrecess, and condoctors 100 are connected to the terminals of thatwinding. Those conductors extend radially inwardly in abutting relationwith one face of the web 88, extend inwardly through the passage 82,extend axially through that passage, and finally extend radiallyoutwardly through the passages in the sleeve 84 to engage the slip rings86. Suitable brushes, notshown, will be mounted adjacent the slip rings86 and can be used to supply current to those slip rings.

Slinge-rs 98 are secured to the portion 80 of increased thickness of thehollow shaft 76; and those slingers are interposed between the web 88and the anti-friction bearings 71 and 72. Those slingers are intended tocause any magnetic particles 104, that tend to work their way into theanti-friction bearings 71 and 72, to be thrown radially outwardly towardthe working gap between stator 60 and the annulus 90. The magnetic linesof force generated by the coil 94 will then be able to attract thosemagnetic particles and to keep them from passing into the anti-frictionbearings 71 and 72. To facilitate a clear showing of therelatively-rotatable parts in FIG. 4, the magnetic particles 104 are notshown in FIG. 4. Those magnetic particles are of standard and usualsize, form and composition; and enough of those magnetic particles areprovided to more than fill the working gap between the stator '60 andthe annulus 90.

A potting compound will be used to help fill the annular recess 92 andto embed the winding 94. That potting compound will keep magneticparticles 104 out of that winding, just as the potting compound 29 ofFIGS. 1 and 2 keeps magnetic particles 56 out of the Winding 28.

The electromagnetic device of FIGS. 3 and 4 is adapted for use as anelectromagnetic clutch; and where that electromagnetic device is used asan electromagnetic clutch, a rotatable shaft, not shown, will betelescoped within the hollow shaft 76 and suitably locked in that hollowshaft by a key within the keyway 78 and by a set screw 79 within thethreaded opening 81. The housing 62 will be suitably mounted so it canrotate; and a belt will be passed around the sheave-like projection 67and around a sheave on a driven member. As long as the winding 94remains de-energized the shaft, not shown, Within the hollow shaft 76will be able to rotate freely relative to the housing. However, ascurrent is caused to flow through the winding 94, that winding willdevelop magnetic flux lines which will pass from the annulus 90 acrossthe working gap into the stator 60, will pass through that stator untilthey are adjacent the opposite side of the coil 94, and will thenre-enter the annulus 90. As those flux lines move through the workinggap between the stator 60 and the annulus 90, they will pass through themagnetic particles in that working gap and will cause those punched andwill then be assembled in face-to-face relation. The web 88 and theslingers 98 will be suitably secured to the hollow shaft 76; and thenthat web will be brazed into engagement with the inner periphery 'of theannulus 90. The inner races [of the anti-friction bearings 71 and 72will then be passed onto the ends of the hollow shaft 76. The winding 94will then bewound into the annular recess 92 within the annulus 90; andthe conductors 100 will be passed through the openings in a couple ofthe laminations of the annulus and then passed inwardly in abuttingrelation with a face of the web 88 and'into the passage 82 in the hollowshaft 76. The ends of those conductors will then be threaded through thepassages in the sleeve 84; and thereafter that sleeve will be telescopedonto the left-hand end of the hollow shaft 76. The ends of thoseconductors can then be suitably secured, as by solder, to the slip rings86.,

The set screw 85 will then be used to fixedly lock the sleeve 84 againstrotation relative to the hollow shaft 76.

The various laminations of the stator 60 will be suitably assembledtogether to form an annulus, and then disposed within the housing 62.Thereafter, the end plate 66 can be pressed into position with itsperiphery engaging the inner surface of the stator 60. The router raceof the anti-friction bearing 72 can then be telescoped inwardly throughthe open left-hand end of the housing 62 until it telescopes within thesocket 70 of that end plate. Thereafter, the end plate 64 can have thesocket 68 thereof telescoped over the sleeve 84 and telescoped into itwill be noted that the masses of those annuli are small.

As a result, the moments of inertia of the rotating parts of tllileelectromagnetic devices of the present invention: are sma Theelectromagnetic devices provided by the present invention can beenergized with alternating current or with direct current. Where theelectromagnetic devices of FIGS. 1 and 2 and of FIGS. 3 and 4 areenergized with alternating current, the time constants thereof will beshorter than they will be when those electromagnetic devices areenergized with direct current.

It will be noted that the only gap, for the magnetic flux lines in theelectromagnetic device of FIGS. 3 and 4, in the direction of flow ofthose flux lines is the working gap between the stator 68 and theannulus 90. As a result, the electromagnetic device of FIGS. 3 and 4 iscompletely free of the additional gaps commonly found in electromagneticdevices which use magnetic particles. The elimination of additional gapsfrom the stator 60 and annulus reduces the amount of power needed tooperate that electromagnetic device. The laminating of the stator 60 andof the annulus 90 and the use of a thin web to support that annulus havemade it possible to provide 9 a time constant for the electromagneticdevice of FIGS. 3 and 4 which is much shorter than the time constant ofa conventional electromagnetic device using magnetrc particles.

In FIGS. 1 and 2 a thin web 48 is disposed adjacent the center of therotor; and in FIGS. 3 and 4 a thin web 88 is disposed adjacent thecenter of the rotor. However, if desired, the web 48 could be replacedby two even thinner Webs at the opposite ends of the thick portion 46 ofthe hollow shaft 42. Similarly if desired, the web 88 could bereplacedby two even thinner webs at the opposite ends of the thickportion 80 of the hollow shaft 76.

In the electromagnetic devices of FIGS. 1 and 2 and of FIGS. 3 and 4,the working gaps are cylindrical in form and extend axially of therotors. If desired, the electromagnetic device of FIGS. 3 and 4 could bemodified so the working gap thereof was circular in form and extendedradially of the rotor. For example, the lamina tions of the stator 60could be rotated ninety degrees so the long axes thereof wereradially-directed rather than axially-directed. Similarly, thelaminations of the annulus 90 could be rotated ninety degrees so thelong axes thereof were radially-directed rather than axially directed.The laminations of the stator 60 would then form a wide, annular facethat could confront a wide, annular, windingcontaining face of theannulus 60. Those faces would be mounted immediately adjacent each otherand would define the working gap for the electromagnetic device. Thewinding would generate magnetic lines of flux; and those lines of fluxwould pass through that working gap and through the magnetic particlestherein to cause those magnetic particles to apply forces to that statorand to that annulus.

In the foregoing description, the inner member of each electromagneticdevice has been referred to as a rotor, and the outer member of eachelectromagnetic device has been referred to as a stator. However, whilethe outer member 60 in FIGS. 3 and 4 has been described as a stator,that member is intended to, and does, rotate. Hence it will beunderstood that the word stator refers to a member which is mountedadjacent a rotor and which may or may not rotate.

In reducing the time constants of electromagnetic devices, such aselectromagnetic clutches or electromagnetic brakes which use magneticparticles, the present invention has made it possible to use alternatingcurrent to operate those electromagnetic devices. Prior electromagneticdevices, such as electromagnetic clutches or electromagnetic brakeswhich used magnetic particles had such long time constants that theycould not respond to the alternations of fifty cycle and sixty cyclealternating current. As a result, those prior electromagnetic devices,such as electromagnetic clutches or electromagnetic brakes which usedmagnetic particles, were limited in application. The electromagneticdevices of the present invention are, however, not so limited-beingcapable of being operated by alternating current as well as by directcurrent.

In the electromagnetic device of FIGS. 1 and 2, the potting compound 29defines a wear-resisting annulus that will keep the magnetic particles56 out of the winding 28. If desired, however, the end turns of thatwinding could be covered and encased by tape to keep those magneticparticles out of that winding. Also, if desired, tubes or sleeves ofnon-magnetic metal, of formica, of plastic, or of other material whichhad outer diameters that were slightly smaller than the inner diametersof the end turns of the winding 28, could be telescoped within those endturns and used to span the spaces between the inner faces of the endplates 30 and 32 and the end faces of the stator 22. Those tubes orsleeves would then keep the magnetic particles out of that winding.

Whereas the drawing and accompanying description have shown anddescribed two preferred embodiments of the present invention it shouldbe apparent to those skilled in the art that various changes may be madein the form of the invention without affecting the scope thereof.

What I claim is:

1. An electromagnetic device that comprises:

(a) a rotor,

(b) a stator,

(c) said rotor and said stator having confronting portions that arespaced apart to define a working gap,

((1) a housing that encloses said working gap and said confrontingportions of said rotor and stator and that holds magnetic particlesavailable to said working (e) earings that permit relative rotationbetween sard rotor and said stator,

(f) a web that supports said confronting portion of said rotor,

(g) an annular recess in said confronting portion of said rotor,

(h) a winding that is disposed within said annular recess and thatresponds to the flow of current therethrough to cause magnetic lines offlux to pass through said working gap between said rotor and saidstator, and

(i) a shaft that supports said web,

(j) said magnetic particles responding to said magnetic lines of flux tomove into said working gap and apply forces to both said rotor and saidstator,

(k) said rotor having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(1) said laminations being parallel to the axis of said shaft,

(m) said stator having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(11) said laminations of said stator being parallel to said axis of saidshaft,

(0) said confronting portion of said stator being completely free of airgaps in the direction of flow of said magnetic lines of flux,

(p) said confronting portion of said rotor being completely free of airgaps in the direction of flow of said magnetic lines of flux,

(q) whereby said winding can apply flux lines of substantiallyundiminished strength to said working gap,

(r) said web being narrow and being intermediate the ends of saidconfronting portion of said rotor, whereby said confronting portion ofsaid rotor is cantileverlike relative to said web.

2. An electromagnetic device that comprises:

(a) a rotor,

(b) a stator,

(c) said rotor and said stator having confronting portions that arespaced apart to define a working gap,

(d) a housing that encloses said working gap and said confrontingportions of said rotor and stator and that holds magnetic particlesavailable to said working gap, and

(e) a winding that responds to the flow of current therethrough to causemagnetic lines of flux to pass through said working gap between saidrotor and said stator,

( f) said magnetic particles responding to said magnetic lines of fluxto move into said working gap and apply forces to both said rotor andsaid stator,

(g) said rotor having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(h) said stator having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(i) said confronting portion of said stator being substantially free ofair gaps in the direction of flow of said magnetic lines of flux,

(j) said confronting portion of said rotor being substantially free ofair gaps in the direction of flow of said magnetic lines of flux,

(k) whereby said winding can apply flux lines of substantiallyundiminished strength to said working p,

(I) said laminations of said stator extending axially of said stator,

(In) said laminations of said rotor extending axially of said rotor.

3. An electromagnetic device that comprises:

(a) a rotor,

(-b) a stator,

(c) said rotor and said stator having confronting portions that arespaced apart to define a working gap,

(d) a housing that encloses said working gap and said confrontingportions of said rotor and stator and that holds magnetic particlesavailable to said working gap, and

(e) a winding that responds to the flow of current therethrough to causemagnetic lines of flux to pass through said working gap between saidrotor and said stator,

( f) said magnetic particles responding to said magnetic lines of fluxto move into said working gap and apply forces to both said rotor andsaid stator,

(g) said rotor having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(h) said stator having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(i) said laminations of said stator extending axially of said stator,

(j) said laminations of said rotor extending axially of said rotor.

4. An electromagnetic device that comprises:

(a) a rotor,

(b) a stator,

(c) saidrotor and said stator having confronting portions that arespaced apart to define a working gap,

(d) a housing that encloses said working gap and said confrontingportions of said rotor and stator and that holds magnetic particlesavailable to said working gap, and j (e) a winding that responds to theflow of current therethrough to cause magnetic lines of flux to passthrough said working gap between said rotor and said stator,

(f) said magnetic particles responding to said magnetic lines of flux tomove into said working gap and apply forces to both said rotor and saidstator,

(g) an annular recess in said rotor,

(h) said winding being disposed within said annular recess,

(i) said confronting portions of said rotor and stator being laminatedto enable said electromagnetic device to have a short time constant,

(j) the laminations of said rotor and stator being directed transverselyof said annular recess in said rotor.

5. An electromagnetic coupling device that comprises:

(a) a rotor,

(b) a stator,

(c) said rotor and said stator having confronting portions that arespaced apart to define a working gap,

(d) said rotor having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(e) said stator having the confronting portion thereof formed from aplurality of laminations of magnetic material,

(f) one of said confronting portions having a multiplicity of slotstherein distributed substantially uni- 12 formly along the length ofsaid confronting portion, (g) a housing that encloses said working gapand said confronting portions of said rotor and stator and that holdsmagnetic particles available to said working gap, and

(h) a winding that is wound within said multiplicity of slots in saidone onfronting portion and that has the end turns thereof projectingoutwardly beyond the ends of said slots,

(i) said winding responding to the flow of current therethrough todevelop a multiplicity of poles that cause magnetic lines of flux topass through said working gap between said rotor and said stator,

(j) said winding having the odd-numbered poles thereof of one polarityand having the even-numbered poles thereof of opposite polarity,

(k) said multiplicity of poles and the alternating of said poles forcingsubstantially all of the lines of magnetic flux generated at one pole topass to and through the adjacent, alternated poles,

(1) said magnetic particles responding to said magnetic lines of flux tomove into said working gap and apply forces to both said rotor and saidstator,

(m)-said multiplicity of poles and the alternating of said poles forcingsubstantially all of said magnetic lines of flux from said winding'toflow through short, generally circular paths in said confronting portionof said rotor and to remain close to said confronting portion of saidrotor,

(11) said multiplicity of poles and the alternating of said polesforcing substantially all of said magnetic lines of flux from saidwinding to flow through short, generally circular paths in saidconfronting portion of said stator and limiting the distance whichsubstantially every magnetic line of flux from said winding flows alongthe circumference of said stator to a value substantially less thanone-half the length of said circumference of said stator,

(0) said winding being the sole source of magnetic flux lines for saidelectromagnetic coupling device and being energized by a source ofcurrent that is wholly external of said electromagnetic coupling deviceand that has a substantially constant voltage, whereby said winding canimmediately generate the magnetic lines of flux for said multiplicity ofpoles and whereby the value of said magneti lines of flux issubstantially independent of the speed of rotation of said rotor,

(p) said laminations in said con-fronting portions of said rotor andstator coacting with the short circular paths for said magnetic lines offlux, caused by said multiplicity of alternated poles, to make the timeconstant for said electromagnetic coupling device a small fraction ofthe time constant of an electromagnetic coupling device of camparabletorque rating which has a non-laminated rotor and stator and whichforces the magnetic lines of flux thereof to flow through elongatedpaths in said rotor and stator.

References Cited by the Examiner UNITED STATES PATENTS 2,575,360 11/1951Raln'now 192-215 2,649,935 8/ 1953 Tack 192'21.5 2,663,809 12/1953Winslow 192-21.5 2,794,525 6/ 1957 Winther 192-215 2,894,407 7/ 1959Brill 19221.5 2,925,896 2/ 1960 Jarschke 192-21.5 2,927,472 3/ 1960Grant 19221.5

FOREIGN PATENTS 1,142,319 3/1957 France.

DAVID J. WILLIAMOWSKY, Primary Examiner.

1. AN ELECTROMAGNETIC DEVICE THAT COMPRISES: (A) A ROTOR, (B) A STATOR,(C) SAID ROTOR AND SAID STATOR HAVING CONFRONTING PORTIONS THAT ARESPACED APART TO DEFINE A WORKING GAP, (D) A HOUSING THAT ENCLOSES SAIDWORKING GAP AND SAID CONFRONTING PORTIONS OF SAID ROTOR AND STATOR ANDTHAT HOLDS MAGNETIC PARTICLES AVAILABLE TO SAID WORKING GAP, (E)BEARINGS THAT PERMIT RELATIVE ROTATION BETWEEN SAID ROTOR AND SAIDSTATOR, (F) A WEB THAT SUPPORTS SAID CONFRONTING PORTION OF SAID ROTOR,(G) AN ANNULAR RECESS IN SAID CONFRONTING PORTION OF SAID ROTOR, (H) AWINDING THAT IS DISPOSED WITHIN SAID ANNULAR RECESS AND THAT RESPONDS TOTHE FLOW OF CURRENT THERETHROUGH TO CAUSE MAGNETIC LINES OF FLUX TO PASSTHROUGH SAID WORKING GAP BETWEEN SAID ROTOR AND SAID STATOR, AND (I) ASHAFT THAT SUPPORTS SAID WEB, (J) SAID MAGNETIC PARTICLES RESPONDING TOSAID MAGNETIC LINES OF FLUX TO MOVE INTO SAID WORKING GAP AND APPLYFORCES TO BOTH SAID ROTOR AND SAID STATOR, (K) SAID ROTOR HAVING THECONFRONTING PORTION THEREOF FORMED FROM A PLURALITY OF LAMINATIONS OFMAGNETIC MATERIAL, (L) SAID LAMINATIONS BEING PARALLEL TO THE AXIS OFSAID SHAFT, (M) SAID STATOR HAVING THE CONFRONTING PORTION THEREOFFORMED FROM A PLURALITY OF LAMINATIONS OF MAGNETIC MATERIAL, (N) SAIDLAMINATIONS OF SAID STATOR BEING PARALLEL TO SAID AXIS OF SAID SHAFT,(O) SAID CONFRONTING PORTION OF SAID STATOR BEING COMPLETELY FREE OF AIRGAPS IN THE DIRECTION OF FLOW OF SAID MAGNETIC LINES OF FLUX, ( P) SAIDCONFRONTING PORTION OF SAID ROTOR BEING COMPLETELY FREE OF AIR GAPS INTHE DIRECTION OF FLOW OF SAID MAGNETIC LINES OF FLUX, (Q) WHEREBY SAIDWINDING CAN APPLY FLUX LINES OF SUBSTANTIALLY UNDIMINISHED STRENGTH TOSAID WORKING GAP, (R) SAID WEB BEING NARROW AND BEING INTERMEDIATE THEENDS OF SAID CONFRONTING PORTION OF SAID ROTOR, WHEREBY SAID CONFRONTINGPORTION OF SAID ROTOR IS CANTILEVERLIKE RELATIVE TO SAID WEB.